In Ms. Q’s deck of cards, every card is one of colors (red, green, blue, and yellow), and is labeled with one of numbers (1, 2, 3, 4, 5, 6, 7 ). Among all the cards of each color, there is exactly one card labeled with each number. A group of cards from this deck is considered to be two pair if it contains two cards with the same number, and two cards with another, different number.
Yunseol draws cards from Ms. Q's deck. What is the probability that the group of cards Yunseol draws is two pair? What about for one pair?
(hints: use constructive counting)